This museum is free to enter just like any other Smithsonian but parking is $15.
But don't let that bother you because you are in for a day worth of treat (There is McD inside).
There is an IMAX inside as well and they honor previous IMAX purchases from other Smithsonian museums to give you discount tickets. This always works out best because they have pretty good shows going on year round.
The museum is inside a giant hanger and has over 300 air crafts on display and a space shuttle (Discovery), tons of bombs/missiles/rockets and satellites. There are enough information cards next to exhibits.
The arrangements is done to maximize the space utilization and may feel like cramped up because there are air crafts hanging over head in more than two levels.
The best part is they have free guided tours. They are few elderly guides but they are always busy. Do get in line to register for free tour or just tag along a session in progress.
This is a best thing for kids because they can enjoy the museum without parents having to explain them everything. The ramp levels work out the best to get the best view of floor and take some good snaps with unique views.
The space shuttle is main attractions located near the "black bird" where people like to hang out the most.